The invention relates to a contact structure in an electromagnetic shielding, by which the interior of a housing is electromagnetically shielded from the outside.
The xe2x80x9chousingxe2x80x9d according to this invention can be a building, a living or work container, a living or working unit in the form of a container, a vehicle body, or other structure comprising an inner space. The invention relates to such a housing which is provided with an electrically conductive layer. Typically the walls of the housing may have aluminium slabs forming the surfaces of the walls and being separated by, for example, a heat- and sound insulating intermediate layer. Aluminium profiles are provided at the edges and end faces of the wall parts electrically conductively connected to the aluminium slabs.
Very often it is necessary to xe2x80x9celectrically shieldxe2x80x9d an inner space. The entering of electromagnetic fields into the inner space of the housing from the outside shall be prevented. Such fields can disturb instruments, for example measuring instruments, which are used in the inner space. This leads to malfunctioning or wrong measurement results. Such an electromagnetic shielding is achieved by an electrically conductive layer on the wall. Such electromagnetic fields, however, can undesirably enter through openings, for example doors or window openings, into the inner space. These openings are closed by appropriate closing elements, such as doors, windows, flaps or the like. These closing elements are also provided with an electrically conductive layer. In order to achieve electromagnetic shielding, it is necessary to conductively connect these electrically conductive layers of the closing elements with the electrically conductive layer of the wall without interruptions. Some sort of xe2x80x9celectromagnetic sealxe2x80x9d is required.
It is known to glue, screw or clamp contacts between the wall and the closing element. The known ways of fixing are expensive and unsafe.
It is an object of the invention to provide a simply assembled contact assembly of the above mentioned kind for the electric connection of conductive layers of the wall and a closing element of the housing.
To this end, a contact structure is provided in an electromagnetic shielding, by which the interior of a housing is electromagnetically shielded from the outside. The housing has walls, at least one opening in one of the walls and a closing element adapted to optionally open and close this opening. The housing and the closing element each have an electrically conductive shielding layer. The contact structure serves to establish electric contact between the shielding layers of the housing and the closing element. The contact structure comprises electric contact means at one of the parts, either the wall or the closing element, conductively connected to the conductive layer of this part. The contact means, when the opening is closed by the closing element, extends around the opening for establishing electric contact between the conductive layer of this one part with the conductive layer of the other one of the parts. This one of said parts has a circumferential groove in an end face around the opening. This groove having inwardly projecting longitudinal ledges , whereby a circumferential cavity is defined by the groove and the ledges. This cavity is open through a slot between the ledges. The ledges are recessed at, at least, one location along the slot to define an opening wider than the slot to permit insertion of the contact means therethrough. The contact means have side portions which, after such insertion and longitudinal displacement in the cavity, are held in place by the ledges.
The contact means are therefore form-fittingly held in the circumferential groove by the inwardly projecting ledges of the circumferential groove. No glueing or screwing operations are required. The inserting of the contact means into the circumferential groove is achieved by recesses, for example millings, through which the contact means can be inserted into the circumferential groove.
In a preferred embodiment of the invention the conductive layers of the wall and of the closing element are formed on the surfaces of the wall and the closing element, respectively. The circumferential groove is formed in such a conductive surface of one part, for example the closing element. The contact means resiliently engage the conductive surface of the other part, for example the wall, when the closing element is closing the opening. The electric contact is then easily established by contacting the contact means to the conductive surface of the parts.
The contact means are preferably formed by a strip-shaped profile from resilient, electrically conductive material guided in the circumferential groove with a foot portion retained by the ledges of the circumferential groove. The profile is provided with a curved contact portion attached to one side of the foot portion and projecting from the circumferential groove with its free end. Preferably the curved contact portion has a bell-shaped cross section.
The foot portion may be a continuous sheet steel strip while the curved contact portion attached thereto is divided in individual sections by transverse cuts, the individual sections being connected by the continuous sheet steel strip. Thereby the individual sections can individually contact the contact surfaces of the other part and compensate for possible unevenness of those contact surfaces.
Typically the opening is a rectangular door- or window opening. A recess for inserting the contact means is provided in each longitudinal and transversal edge of the door- or window opening or door or window, respectively. The contact means are formed by a contact strip for each longitudinal or transversal edge.
Preferably complementary profile elements are provided around the opening and the closing element, the profile elements having end faces facing each other, when the opening is closed, which form an angle with the surfaces of the housing or the closing element, respectively. The circumferential groove is provided in one of these inclined end faces, while the contact means resiliently engage the other one of these inclined surfaces. Thereby one component of the closing force of the closing element acts on the contact means when the opening is closed.